I'm not sure if its me, but I have some problems with the 16.04 live CDs. See for yourself (using VirtualBox):
VirtualBox settings: Base Memory: 3000MB Processors: 1 Video Memory: 128MB No 3D Acceleration enabled.
The strange thing is that I tried Kubuntu 16.04 live CD on a HP Touchsmart 14 laptop and the same thing happened. It didn't happen with Xubuntu 16.04 (same laptop). What can be the problem?
To fix this press right ctrl+f2 to go into TTY then you can switch back with right ctrl+f1, this sorts the resolution problem.
Mac Keyboard User
I had the same issue trying to install Ubuntu 16.04 on virtual machine in VirtualBox 5.0.22 installed on my macbook pro 13 mid 2013.
I was not able to emulate the right ctrl with my keyboard therefore I opted for Luis Alvarado and Whaaaat's solution: in the VM Settings (under the System tab), activate the Enable EFI checkbox having care of selecting PIIX3 chipset as a option.
When the installation process was completed, I disabled the EFI option and It worked like a charm.